An apparatus for the manufacture or working, in particular grinding, of the tooth system of spur gears is already known. This apparatus is provided with a rotating gearlike tool, which mates with the workpiece tooth system at a crossed-axes angle of larger than 35.degree.. The tool is formed hyperboloidally or similarly and is at least as wide as the workpiece tooth system (German AS No. 25 16 059).
The basic purpose of the invention is to improve the work result of such an apparatus.
The basic purpose of the invention is attained with an apparatus utilizing a pair of guide wheels located adjacent a tool and workpiece, which guide wheels guide the tool's working of the workpiece. With the term "abrasive surface" is meant a chip-removing surface on a tool which does not have uniformly directed cutting edges or the like. This includes all tools with granular work surface, for example grinding tools, however, also includes tools for the electrolytic or electroerosive or electrochemical material removal. (For example, shaving gears do not fall within this group.)
An apparatus according to the invention operates with single-side contact, namely each tool or workpiece tooth has only one tooth flank in contacting relation during operation. This has the advantage that a cutting feed is possible, during which the center distance between the tool and the workpiece can remain the same without requiring a change of the tooth helix.
A further purpose of the invention is to prevent with certainty the wrong tooth flanks from contacting one another during the working operation.
This purpose is attained by an apparatus utilizing a braking device to retard the movement of one of the tool and workpiece relative to the driving action provided on the other of the tool and workpiece.
Various embodiments of the apparatus according to the invention are possible. For example, it is possible to use for the guide wheels friction wheels or friction disks or the like, the manufacture of which is relatively simple. One must only make sure that they have the correct speed ratio.
Another embodiment is the use of gears as guide wheels. Here too one must only make sure that the speed ratio is correct. The pitch circles of the meshed tool-workpiece and of the guide wheel pair do not need to agree; to the contrary, it can even be favorable if they are different, because then possibly pitch errors, which are caused by the apparatus, are balanced out.
If the apparatus according to the invention is used in a mass manufacture operation, it would be possible to use a first special machine for working the right flank and a second special machine for working the left flank of the workpiece teeth. Since these machines are then usually inserted into a line of machines, the total work time is not increased through this type of procedure, on the other hand the apparatus would be simple, inexpensive and not susceptible to breakdown. However, the investment costs are less as a whole if the invention includes a control device for changing the relative position of the tooth flanks on the tool and workpiece.
A further favorable development of the invention is to not only intend the engagement of the tooth system of the tool and the workpiece, but also the possibility of a one-time and step-by-step radial feeding during the actual operation. Using this procedure, it is possible to successfully do away with periodic (wave-shaped) errors of the tooth profile, which can be created in elevational direction, or those which can be created by projecting grinding granulates.
A further important development results from providing a control apparatus which enables a control of the contact pressure between the tool teeth and the workpiece teeth. This further development serves also to increase the work quality.
A favorbble development of the invention results from providing backlash between the meshed guide wheels, because cutting feed can occur without necessitating the center distance to be changed.
The invention is favorably further developed with the backlash feature mentioned above, because with this an effect can be achieved, which is similar to the so-called rigging test stand. The torsion spring offers the possibility of controlling the contact pressure of the working tooth flanks on the workpiece flanks and possibly to make the changing of the tooth flanks more gradual.
A further improvement of the workpiece quality, in particular with respect to the periodic deviations on the workpiece tooth flank, results from providing the guide wheels with different contact pitches than the tooth system of the tool.
The changing of the apparatus according to the invention is made easier by providing change gears, whereby change gears are to be understood to be such gears or friction gears which, similar to the change gears of lathes, are easily exchangeable. In this connection reference is made to the usability of the conventional quadrant.
In order to make the adjusting of the workpiece-tool tooth flanks relative to the guide wheel tooth flanks easier or in order to provide the possibility of automating this adjustment, the invention can be further developed with a drive motor coupled to the tool spindle or the workpiece spindle and a shiftable coupling provided on the spindle separate from the motor.
In order to prevent in the working method with the inventive apparatus the flank abutment from changing unintentionally, and with the provision of a shiftable clutch, the invention can be further developed by providing the spindle which is coupled with the motor with an additional brake or a centrifugal mass.
A further advantageous development is offered by coating at least one of the guide wheels with a material different from the material of the guide wheels. That is, the working surface, namely thus in friction wheels the friction surface or in gears the tooth flank or any other working surface, can be coated with a wear-resistant material, for example titanium nitride or hard chromium or the like or with a material, for example plastic, which has a good sliding characteristic. Preferably both surfaces which work on one another are coated. Advantageous is also a coating material, which is both wear-resistant and also has good sliding characteristics.
A further advantageous development is the provision of a protective device, such as a housing, which surrounds the guide wheels or a plate between the guide wheel pair and the intermeshed workpiece-tool, which plate deflects spray and chips. It may also be a combination of both.
According to a further development, the direction of rotation is changed for changing the flanks which contact each other, the relative sliding of the tooth flanks on one another in direction of the whole depth of the tooth also changes. This means, depending on which axis of the intermeshed tool-workpiece is the driving one, that the relative movement goes from the addendum to the dedendum or vice versa ("chiselling" or "drawing").
It is also possible to effect a changing of the abutting relation without a change in the direction of rotation of the drive to thereby make the working time possibly shorter, however, the work result is possibly not as good as in the case of a change in the direction of rotation. Furthermore, in this method the bending of the teeth must be considered, if high work qualities are demanded.
A further advantage of the invention is that the contact of the right and left workpiece flank with the corresponding tool flank is found quicker, securer and exacter than in conventional machines, namely independent of a changing tooth thickness of the tooth system of the workpiece and independent of the respective wear condition of the tool teeth.
The prepositioning of the workpiece tooth in relationship to the tool tooth space is simple. A prechosen amount can precisely be removed from the workpiece flank, and not time dependently. That which has been stated above is also valid for the dressing of the tool with a dressing wheel.
A particular advantage of the invention is that the amount of the work removal can be predetermined. It is no longer alone dependent on the work time. The tool is carefully treated since during starting and braking the flanks do not contact one another.
In the apparatus according to the invention, the working operation is not interrupted, therefore the pressure of the tool flank on the workpiece flank is approximately equal with the working pressure. Also during the braked or retarded working phase, the flank contact is not interrupted.
The invention operates with a so-called single-side contact. This means that in each case only the one side of the teeth are in contacting engagement. However, it is an important characteristic of the invention that the entirety of the gearing which consists of work tooth system and guide tooth system works with two-flank engagement. This means if in the work tooth system for example the right tooth side contacts, then in the guide tooth system at the corresponding tooth the left tooth side contacts or vice versa. From this results a rigid connection between the workpiece and the tool. Thus, it is prevented with certainty that the tooth flanks can lift off due to vibrations or other influences. Also through this a cutting is possible in a simple manner namely by reducing the center distance, without providing for this a special kinematics, which would be needed if the guide wheels would run without clearance. On the other hand, the single-side contact in the work tooth system assures that the flanks of the work tooth system substantially abut only on the raised flank parts and work at that location.
In the sense of the invention the term of a "motor, which can be changed for both directions of rotation" includes also an arrangement with two apparatus, of which each is specially provided for the working of only one tooth side (flank), and of which the one motor runs in the one direction of rotation and the other one in the other direction of rotation. Changing is done then by transporting the workpiece from tool to tool.
The intermeshed guide wheels should have a contact ratio which is as large as possible. The limit of the possible correction of the teeth is for this the approach of the guide wheels' teeth to become pointed at their crests.
Often on the workpieces more or less must be removed on one tooth flank than on the other. It is a particular advantage that, with the apparatus according to the invention, the material removal for each tooth side can be individually adjusted.
The invention is not to be limited to externally toothed gears, but can be applied also to internally toothed gears.